perf(inject/host): dedup the DualSense HID-output feedback plane (G17)

A game's DualSense output report bundles rumble + lightbar + player-LEDs
+ adaptive-triggers into one report, so a pad that is merely rumbling
re-sends its unchanged lightbar / LED / trigger state on every output
report. The managers already dedup rumble, but forwarded every rich
`HidOutput` event verbatim — flooding the 0xCD feedback plane to the
client during continuous rumble.

Add a shared `HidoutDedup` (dualsense_proto, used by both the Linux UHID
and Windows UMDF managers) that forwards Led/PlayerLeds/Trigger only on a
value change (per side for the two triggers) and always forwards one-shot
TrackpadHaptic pulses — mirroring the rumble dedup two lines above and the
DS4 backend's lightbar dedup. Reset per pad on create/unplug.

Verified on Linux .21 (clippy -D warnings clean, new HidoutDedup unit
test + full suite green); Windows .173 with the rest of Phase 3.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/inject/linux/dualsense.rs

@@ -13,7 +13,7 @@
 //! UMDF-driver backend; this module is just the `/dev/uhid` plumbing around it.
 
 use super::dualsense_proto::{
-    parse_ds_output, serialize_state, DsFeedback, DsState, DS_FEATURE_CALIBRATION,
+    parse_ds_output, serialize_state, DsFeedback, DsState, HidoutDedup, DS_FEATURE_CALIBRATION,
     DS_FEATURE_FIRMWARE, DS_FEATURE_PAIRING, DS_INPUT_REPORT_LEN, DS_PRODUCT, DS_TOUCH_H,
     DS_TOUCH_W, DS_VENDOR, DUALSENSE_RDESC,
 };
@@ -178,6 +178,9 @@ pub struct DualSenseManager {
     state: Vec<DsState>,
     /// Last rumble forwarded per pad, so a report that only changes the LED doesn't re-send it.
     last_rumble: Vec<(u16, u16)>,
+    /// Last rich feedback (lightbar / player LEDs / adaptive triggers) forwarded per pad, so an
+    /// output report that only changed the rumble doesn't re-send unchanged 0xCD feedback.
+    hidout_dedup: Vec<HidoutDedup>,
     /// When each pad last wrote an input report — drives [`DualSenseManager::heartbeat`], which
     /// re-emits the current state during input silence so the kernel never sees the device go quiet.
     last_write: Vec<Instant>,
@@ -201,6 +204,7 @@ impl DualSenseManager {
             pads: (0..MAX_PADS).map(|_| None).collect(),
             state: vec![DsState::neutral(); MAX_PADS],
             last_rumble: vec![(0, 0); MAX_PADS],
+            hidout_dedup: vec![HidoutDedup::default(); MAX_PADS],
             last_write: vec![Instant::now(); MAX_PADS],
             gate: PadGate::new(),
             remap: crate::inject::steam_remap::RemapConfig::from_env(),
@@ -226,6 +230,7 @@ impl DualSenseManager {
                         *slot = None;
                         self.state[i] = DsState::neutral();
                         self.last_rumble[i] = (0, 0);
+                        self.hidout_dedup[i].clear();
                     }
                 }
                 if f.active_mask & (1 << idx) == 0 {
@@ -314,6 +319,7 @@ impl DualSenseManager {
                 self.pads[idx] = Some(p);
                 self.state[idx] = DsState::neutral();
                 self.last_rumble[idx] = (0, 0);
+                self.hidout_dedup[idx].clear();
                 self.last_write[idx] = Instant::now();
                 self.gate.on_success();
             }
@@ -346,8 +352,12 @@ impl DualSenseManager {
                 }
             }
             for h in fb.hidout {
+                // Skip rich feedback that repeats the last-forwarded value (the game's output report
+                // re-sends unchanged lightbar/LED/trigger state alongside every rumble update).
+                if self.hidout_dedup[i].should_forward(&h) {
                     hidout(h);
                 }
             }
         }
     }
+}

crates/punktfunk-host/src/inject/proto/dualsense_proto.rs

@@ -445,10 +445,119 @@ pub fn parse_ds_output(pad: u8, data: &[u8], fb: &mut DsFeedback) {
     }
 }
 
+/// Per-pad dedup for the DualSense HID-output feedback plane (0xCD). A game's DualSense output report
+/// bundles rumble + lightbar + player-LEDs + adaptive-triggers into one report, so a pad that is
+/// merely *rumbling* re-sends its (unchanged) lightbar / LED / trigger state on every output report.
+/// The managers already dedup rumble; this does the same for the rich [`HidOutput`] feedback so the
+/// 0xCD plane carries only genuine changes. State (`Led` / `PlayerLeds` / `Trigger`) is deduped by
+/// value; a one-shot `TrackpadHaptic` pulse is always forwarded (each pulse must fire).
+#[derive(Clone, Default)]
+pub struct HidoutDedup {
+    led: Option<(u8, u8, u8)>,
+    player_leds: Option<u8>,
+    /// Last-forwarded adaptive-trigger effect per side: `[0]` = L2, `[1]` = R2.
+    trigger: [Option<Vec<u8>>; 2],
+}
+
+impl HidoutDedup {
+    /// Forget all remembered state — call when a pad is created or unplugged so the first feedback
+    /// after a (re)connect is always forwarded.
+    pub fn clear(&mut self) {
+        *self = HidoutDedup::default();
+    }
+
+    /// Whether `h` should be forwarded: `true` for a genuine change (remembering the new value) or a
+    /// one-shot pulse; `false` if it repeats the last-forwarded value for its kind.
+    pub fn should_forward(&mut self, h: &HidOutput) -> bool {
+        match h {
+            HidOutput::Led { r, g, b, .. } => {
+                let v = Some((*r, *g, *b));
+                if self.led == v {
+                    false
+                } else {
+                    self.led = v;
+                    true
+                }
+            }
+            HidOutput::PlayerLeds { bits, .. } => {
+                let v = Some(*bits);
+                if self.player_leds == v {
+                    false
+                } else {
+                    self.player_leds = v;
+                    true
+                }
+            }
+            HidOutput::Trigger { which, effect, .. } => {
+                let slot = (*which as usize).min(1);
+                if self.trigger[slot].as_deref() == Some(effect.as_slice()) {
+                    false
+                } else {
+                    self.trigger[slot] = Some(effect.clone());
+                    true
+                }
+            }
+            // One-shot haptic pulse (Steam voice-coil) — state-less, always fires.
+            HidOutput::TrackpadHaptic { .. } => true,
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    /// `HidoutDedup` forwards a value once, drops exact repeats, re-forwards a change, tracks the two
+    /// trigger sides independently, never dedups one-shot haptic pulses, and re-arms after `clear`.
+    #[test]
+    fn hidout_dedup_forwards_only_changes() {
+        let mut d = HidoutDedup::default();
+        let led = |r| HidOutput::Led {
+            pad: 0,
+            r,
+            g: 0,
+            b: 0,
+        };
+        // First value forwards; an exact repeat is dropped; a change forwards again.
+        assert!(d.should_forward(&led(10)));
+        assert!(!d.should_forward(&led(10)));
+        assert!(d.should_forward(&led(20)));
+
+        // Player LEDs dedup on their own field, independent of the lightbar.
+        let pl = |bits| HidOutput::PlayerLeds { pad: 0, bits };
+        assert!(d.should_forward(&pl(0b101)));
+        assert!(!d.should_forward(&pl(0b101)));
+        assert!(!d.should_forward(&led(20))); // lightbar still unchanged
+
+        // The two adaptive triggers (L2=0, R2=1) are tracked separately.
+        let trig = |which, byte| HidOutput::Trigger {
+            pad: 0,
+            which,
+            effect: vec![byte, 0, 0],
+        };
+        assert!(d.should_forward(&trig(0, 1)));
+        assert!(d.should_forward(&trig(1, 1))); // same bytes, other side → still forwards
+        assert!(!d.should_forward(&trig(0, 1)));
+        assert!(d.should_forward(&trig(0, 2))); // L2 effect changed
+
+        // One-shot haptic pulses are never deduped.
+        let haptic = HidOutput::TrackpadHaptic {
+            pad: 0,
+            side: 0,
+            amplitude: 1,
+            period: 2,
+            count: 3,
+        };
+        assert!(d.should_forward(&haptic));
+        assert!(d.should_forward(&haptic));
+
+        // `clear` re-arms every kind.
+        d.clear();
+        assert!(d.should_forward(&led(20)));
+        assert!(d.should_forward(&pl(0b101)));
+        assert!(d.should_forward(&trig(0, 2)));
+    }
+
     /// The Steam dual-pad → DualSense touchpad SPLIT: left pad (surface 1) lands contact 0
     /// on the left half, right pad (surface 2) contact 1 on the right half; y follows the
     /// shared screen convention (top → 0) with no flip; pad clicks set the touchpad-click

crates/punktfunk-host/src/inject/windows/dualsense_windows.rs

@@ -18,8 +18,8 @@
 //! must already be installed; the installer stages it.)
 
 use super::dualsense_proto::{
-    parse_ds_output, serialize_state, DsFeedback, DsState, DS_INPUT_REPORT_LEN, DS_TOUCH_H,
-    DS_TOUCH_W,
+    parse_ds_output, serialize_state, DsFeedback, DsState, HidoutDedup, DS_INPUT_REPORT_LEN,
+    DS_TOUCH_H, DS_TOUCH_W,
 };
 use super::gamepad_raii::{sw_create_cb, PadChannel, SwCreateCtx};
 use crate::gamestream::gamepad::{GamepadEvent, MAX_PADS};
@@ -341,6 +341,9 @@ pub struct DualSenseWindowsManager {
     pads: Vec<Option<DsWinPad>>,
     state: Vec<DsState>,
     last_rumble: Vec<(u16, u16)>,
+    /// Last rich feedback (lightbar / player LEDs / adaptive triggers) forwarded per pad, so an
+    /// output report that only changed the rumble doesn't re-send unchanged 0xCD feedback.
+    hidout_dedup: Vec<HidoutDedup>,
     last_write: Vec<Instant>,
     /// Create-retry gate: a transient UMDF-channel failure backs off and retries instead of
     /// permanently disabling every pad for the session.
@@ -362,6 +365,7 @@ impl DualSenseWindowsManager {
             pads: (0..MAX_PADS).map(|_| None).collect(),
             state: vec![DsState::neutral(); MAX_PADS],
             last_rumble: vec![(0, 0); MAX_PADS],
+            hidout_dedup: vec![HidoutDedup::default(); MAX_PADS],
             last_write: vec![Instant::now(); MAX_PADS],
             gate: PadGate::new(),
             remap: crate::inject::steam_remap::RemapConfig::from_env(),
@@ -386,6 +390,7 @@ impl DualSenseWindowsManager {
                         *slot = None;
                         self.state[i] = DsState::neutral();
                         self.last_rumble[i] = (0, 0);
+                        self.hidout_dedup[i].clear();
                     }
                 }
                 if f.active_mask & (1 << idx) == 0 {
@@ -466,6 +471,7 @@ impl DualSenseWindowsManager {
                 self.pads[idx] = Some(p);
                 self.state[idx] = DsState::neutral();
                 self.last_rumble[idx] = (0, 0);
+                self.hidout_dedup[idx].clear();
                 self.last_write[idx] = Instant::now();
                 self.gate.on_success();
             }
@@ -496,8 +502,12 @@ impl DualSenseWindowsManager {
                 }
             }
             for h in fb.hidout {
+                // Skip rich feedback that repeats the last-forwarded value (the game's output report
+                // re-sends unchanged lightbar/LED/trigger state alongside every rumble update).
+                if self.hidout_dedup[i].should_forward(&h) {
                     hidout(h);
                 }
             }
         }
     }
+}